1. Field of the Invention
This invention relates to a process unit removably mountable on the main body of an image formation apparatus and integrally having an image bearing member and a part or the whole of process means for acting on the image bearing member, and to an image formation apparatus using such kit.
2. Description of the Prior Art
Description will hereinafter be made with an electrophotographic copying apparatus taken as an example of the image formation apparatus.
An electrophotographic copying apparatus has required interchange of the photosensitive medium as the image bearing member, supply of developer, discard of waste toner, cleaning of corona wire, interchange or adjustment of various expendable parts, etc. to be effected periodically, and these have heretofore been carried out by expert service men. Accordingly, a service man must go to the user's office or the like each time his service is needed and this has been very cumbersome.
Therefore, recently, as shown in U.S. Pat. No. 3,985,466, it has been considered to construct a kit in which image formation means such as a photosensitive drum, a developing device, a cleaner, a charger, etc. are made into a unitary structure and to interchange the various units at a time during interchange of the photosensitive drum, thereby reducing the maintenance work. By adopting the above-described construction, the user can simply interchange each process unit, also referred to as a process kit, which particularly requires periodical maintenance, thus reducing the maintenance work to be done by the service man. Further, by interchanging the kit with a process kit which contains toner of other color, formation of colored images becomes possible. Alternatively, by interchanging the kit with a process kit which incorporates other developing means, the user can use developing means corresponding to the original image to be copied.
However, when the kit is interchanged or when the kit is removed from the apparatus body, the hand may touch the photosensitive drum held by the kit to stain or injure the drum. Possibly, the photosensitive drum having, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer as the image bearing member held by the kit may be exposed to light with a result that the photosensitive layer is deteriorated. The injury or stain on the photosensitive drum or the deterioration of the photosensitive layer may adversely affect the formed images.
Particularly, where a process kit is used, the kit is often interchanged for the purpose of preservation or for the purpose of interchange with a process kit containing therein toner of another color as previously described, even during a period in which the kit is usable, and therefore it is necessary to positively protect the photosensitive drum.